1. Field of the Invention
The present invention relates generally to an optical storage device, and more particularly to a magneto-optical disk drive having an optical head and a magnetic head.
2. Description of the Related Art
A magneto-optical disk drive is required to become higher in recording density year after year, and various methods have been developed for recording of information in a magneto-optical disk drive. According to an optical modulation method adopted by the ISO standard, a laser beam is modulated by data to be recorded as applying an external magnetic field in a fixed direction, thereby recording information on a magneto-optical recording medium. In this optical modulation method, a recording density of information is limited by the size of a beam spot.
In contrast, a magnetic field modulation method such that an external magnetic field is modulated by data to be recorded as directing a laser beam having a fixed intensity is considered to have an advantage in high-density recording over the optical modulation method, because a beam spot can be overlapped. The external magnetic field is modulated at a high speed by data to be recorded, and a contact type or flying type magnetic head is therefore used as the magnetic head. The shape and operation principle of the magnetic head in the magneto-optical disk drive are substantially the same as those of a magnetic head used in a magnetic disk drive or a magnetic tape drive. In the flying type, the magnetic head flies a height of about 10 xcexcm above the magneto-optical disk being rotated, and records data in the beam spot. It is considered that there is a large chance of use of a magnetic head also in an optical modulation type magneto-optical disk drive with the advance of high-density recording and reproduction in the future.
The following problems are considered in using a magnetic head in a magneto-optical disk drive.
As a first problem, the magnetic head is difficult to handle as compared with an electromagnet bias used in a conventional optical modulation type magneto-optical disk drive, because the magnetic head flies a height of about 10 ìm above the disk. In particular, it is greatly important to provide means for preventing breakage of the magnetic head due to the contact between the magnetic head and a portable disk or disk cartridge. Conventionally provided is means for lifting the magnetic head or means for retracting the magnetic head outside the disk to prevent the contact between the magnetic head and the disk cartridge in inserting/ejecting the disk cartridge into/from the disk drive. However, there is no special means for preventing breakage of the magnetic head when the disk cartridge is present in the disk drive.
A second problem is that the magnetic head is located opposite to the optical head with respect to the disk. In the conventional disk drive, the magnetic head and the optical head are fixed to the same carriage and moved together. Accordingly, a carriage portion for a magnetic head assembly including a load beam must be set longer than a data region of the disk. In the case of retracting the magnetic head outside the disk to prevent breakage of the magnetic head, the carriage must therefore be moved to a considerably deep position in the disk drive, so that an installation space for optical components in the disk drive is reduced. Accordingly, the disk drive as an optical storage device becomes large in size.
It is therefore an object of the present invention to provide an optical storage device having means for preventing breakage of a magnetic head when an optical storage medium is present in the device.
It is another object of the present invention to provide an optical storage device which can prevent a reduction in installation space for optical components due to the movement of a carriage.
In accordance with an aspect of the present invention, there is provided an optical storage device for making an access to an optical storage medium accommodated in a cartridge, including a drive base; a cartridge holder provided on the drive base for receiving the cartridge; a first carriage mounted on the drive base so as to be reciprocatable in a first direction; a first drive mechanism for moving the first carriage; an optical head mounted on the first carriage for directing light to a given position on the optical storage medium; a second carriage mounted on the cartridge holder so as to be reciprocatable in the first direction; a second drive mechanism mounted on the cartridge holder for moving the second carriage; and a magnetic head assembly mounted on the second carriage and having a magnetic head for applying a magnetic field to a given position on the optical storage medium.
The optical storage device further includes an unloading mechanism for holding the magnetic head in its lifted condition above the optical storage medium in reproducing data. Preferably, the magnetic head is lifted at a position outside of the optical storage medium or at an innermost circumferential portion of the medium.
The magnetic head assembly includes a support member fixed at a base end portion thereof to the second carriage and the magnetic head mounted on a front end portion of the support member. Preferably, the unloading mechanism includes a magnetic head lifter fixed to the cartridge holder and an engaging member fixed to the support member.
Alternatively, the unloading mechanism includes a magnetic head lifter fixed to the cartridge holder and the support member engaging the magnetic head lifter when the magnetic head is moved to an outermost circumferential portion of the optical storage medium.
In accordance with another aspect of the present invention, there is provided an optical storage device for making an access to an optical storage medium, including a drive base; a first carriage mounted on the drive base so as to be reciprocatable in a first direction; a first drive mechanism for moving the first carriage; an optical head mounted on the first carriage for directing light to a given position on the optical storage medium; a second carriage provided independently of the first carriage so as to be reciprocatable in the first direction; a second drive mechanism for moving the second carriage; and a magnetic head assembly mounted on the second carriage and having a magnetic head for applying a magnetic field to a given position on the optical storage medium; the stroke of movement of the magnetic head being longer than the stroke of movement of the optical head.
Preferably, the stroke of movement of the magnetic head is longer than the stroke of movement of the optical head on the inner circumferential side or outer circumferential side of the optical storage medium.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.